diff --git a/src/main/java/serene/simple/Main.java b/src/main/java/serene/simple/Main.java
index bfbcfff..ab608ee 100644
--- a/src/main/java/serene/simple/Main.java
+++ b/src/main/java/serene/simple/Main.java
@@ -1,6 +1,3 @@
-/*
- * This Java source file was generated by the Gradle 'init' task.
- */
 package serene.simple;
 
 import java.io.IOException;
@@ -18,7 +15,7 @@ public class Main {
     }
 
     private static void startRepl() {
-        Environment rootEnv = Environment.getBaseEnvironment();
+        Scope rootScope = Scope.getRootScope();
 
         Console console = System.console();
 
@@ -29,18 +26,27 @@ public class Main {
 
             ByteArrayInputStream inputStream = new ByteArrayInputStream(inputData.getBytes());
             ListNode<Node> nodes = Reader.read(inputStream);
-            ...
+
+            Object result = ListNode.EMPTY;
+
+            for (Node n : nodes) {
+                result = n.eval(rootScope);
+            }
+
+            if (result != ListNode.EMPTY) {
+                System.out.println(result);
+            }
         }
 
     }
 
     private static void runSerene(String filePath) throws IOException {
-        Environment rootEnv = Environment.getBaseEnvironment();
+        Scope rootScope = Scope.getRootScope();
 
         ListNode<Node> nodes = Reader.read(new FileInputStream(filePath));
 
         for (Node n : nodes) {
-            n.eval(rootEnv);
+            n.eval(rootScope);
         }
     }
 }
diff --git a/src/main/java/serene/simple/Reader.java b/src/main/java/serene/simple/Reader.java
new file mode 100644
index 0000000..aa21514
--- /dev/null
+++ b/src/main/java/serene/simple/Reader.java
@@ -0,0 +1,25 @@
+package serene.simple;
+
+import java.io.IOException;
+import java.io.PushbackReader;
+
+
+public class Reader {
+    public static Node readNode(PushbackReader inputStream) throws IOException {
+        char c = (char) inputStream.read();
+        inputStream.unread(c);
+
+        if (c == "(") {
+            return readList(inputStream);
+        }
+        else if (Character.isDigit(c)) {
+            return readNumber(inputStream);
+        }
+        else if (c == ")") {
+            throw new IllegalArgumentException("Unmatch paranthesis.")
+        }
+        else {
+            return readSymbol(inputStream);
+        }
+    }
+}